Method of forming blanks for making seamless tubes



Ma 14, 1929- R. c. STIEFEL 1312372 METHOD OF FORMING BLANKS FOR MAKINGSEAMLESS TUBES Filed Nov. 8, 1927 i l ll? WITNESS 4 F' 5 I INVENTOR jGaba 46%# llatented May 14, 1929.

UNITED STATES BALPH C. STIEFEL, OJF ELLWOOD CITY, PENNSYLVANIA.

METHOD OF FOBMING BLANKS FOR MAKING SEAMLESS TUBES.

Application filed November 8, 1927.

The invention relates to the manufacture ot seamless tubng, and hasparticularly to do with the preparation of blanks for use in suchmanut'acture.

'l`he usual method of forming a blank for the manufacture of seamlesstubing by plug rolling or other processes is to pierce and materiallylengthen a solid billet by revolving it between obliquely-disposedbarrelshaped rolls and force it over a mandrel held against longtudinalmovement but mounted for rotaton with the billet. In some cases,particularly in the manufacture ot' larger sized tubing, .the thuspierced billet is passed through a second pair of obliquelydisposedbarrel-shaped rolls and over a larger mandrel to` further lengthen thebillet, enlarge its diameter, and reduce its ;wall thickness. i

'the barrel-shaped piercing rolls torm a converging enterng pass and adiverging enit pass, and accordingly have their highest peripheralspeeds at the narrowest point ot the pass where the billet is reduced toits smallest diameter. Therefore, the billet is acted upon at diflerenttransverse sections by peripheral roll speeds which are inversely inproportion p of the billet. This condition is very severe on the metal,producing severe distortions ot it and g'reatly aggravating or.developing defects in the billet which cause loss 'of material andincrease the labor and other cost ot production.

'l`hese prej udicial consequences are'greatly magnified in the piercingoperation, or operations, when a second piercing pass is used, hy reasonof the fact that the billets while heing pierced have been materiallyelongated, particularly in the dverging portion ot the pass where theperced billet passes over' the enlarged tapered mandrel. The piercngaction may be Compared to that of a continuous 'rolling mill in whicheach successivo pair of rolls forms a work pass. When a billet is beingpierced each of its diametrical lines comes under compression a numberof times similar to the successive compressions efl'ected by succeedingpairs of rolls in a continuous mill. However, in a continuous mill thesuccessive roll passes are 'tormed to properly take care of the Volumeor section of a work piece or blank in order to eliminate stresses onthe blank between the passes; whereas in a piercing mill in to theangular surface speed Serial No. 231308.

which a billet is materially elongated in the entire pass, and also inwhich the diameter of 'the pierced portion of the billet is enlarged andits wall thiokness diminished, excessive stresses are imposed upon themetal, which stresses greatly magnity those necessarily inherent in apiercing operation by reason of the inversely varying roll speedspreviously explained. Furthermore, these conditions of piercing resultin an excessive Consumption of power, and in a correspondmg increase inOperating expense.

It is well known that billets used tor piercing must be of superiorquality to withstand the punishment to which the metal is subjected byreason of the severe stresses imposed upon thom. When losses occur, thatis to say, when detective tubing is produced, a chaotic conditionarises, the operating management of the tube mill, believing thatworking conditions have been maintained constant and proper, attributesthe losses to defective metal, and the steel manufacturer, believingthat the metal is not defective, attributes the losses to improperconditions in the piercing procedure. Manifestly it is desirable toeliminate one of the causes of detective tubing so that the source ottrouble may be determined.

The object ot 'this invention is to provide a method of forming a blankfor making a seamless tube whereby the stresses imposed on the metal arereduced to a minimuman as a result thereof the power consumptiolessened, the labor cost diminished, the scrap 'losses reduced, and thecause of scrap losses readily determmed.

In the practice of the invention, a blank tor making a seamless tube isformed by progressively piercing a solid billet in such a manner as toeffect a minimum elongation of it. Rather than commencing with arelatively short and thick billet, as is the prevalling practice, I usea billet of relatively increased length and diminished diameter," andelongate it only in the converging portion of a pass between piercingrolls, and there only to the extent necessary to cause suflicient gripupon thebillet by the rolls to force the billet over the point of apiercing mandrel. In the diverging portion of the roll pass the crosssectional area of the then pierced portion of the billet is maintainedconstant, so that the diameter of the billet is increased and its wallthickness diminished' without imposing upon the metal the excessive ingportion of the pass. Also, consider-ing stresses heretofore existingincident to the the pierced portion of the billet in the pass elongatonof the billet in this portion of as extending froni the transverse plane'the`pass. When the pierced billet is again through the point of themandrel to the passed through a piercing nill' to further transverseplane through the points 7, the enlarge its diameter and dininish itswall cross sectional area of the major part of the thickness, this idone with little, if any, pierced portion of the billet is maintainedelongation of the billet in any portion of the uniforn during theexpanding and reducing pass, and with consequent elimination ofoperation. Thus the billet is pierced with a severe stressing of themetal. nininun attending elongation, and with The invention will befurther explained little, if any, elongation in the divcrging withreference to the accompanying drawportion of the piercing pass whereelongation ings, of which Fig. 1 is a View of a pair of stresses areseverest on the metal. barrel-shaped piercing rolls, showing a solidWhen, in the practice of this invention, billet in the process of beingpierced; Fig. 2 the pierced billet 4 of Fig. 4 is acted upon a View of aair of mushroom-shaped rolls to enlarge its diameter and dininish itswall showing a pierced billet in the process of thickness, it ispreferably passed through having its diameter increased and its wall apiercing nill of the type indicated in thickness diminished; Fig. 3 aside View of Fig. 2 as comprising a pair of mushrooma solid billet ofsuch relative proportions as type rolls 10 and a mandrel ll arrangedbemay advantageously be used in the practice tween them, although ifdesired' ba'relof the invention; Fig. 4 a longitudinal censhapedpiercing rolls may be used. By usiw tral sectional view of the billet ofFig. 3 after mushroon-type rather than barrel-shape having been pierced'by the nill of Fig. 1; rolls, the peripheral speeds of the rolls at andFig. 5 a longitudinal central sectional their various points in thediverging porview of the billet of Fig. 4 after having tion of thepiercing pass corresponds in passed through the mill of Fig. 2. generalto the angular speed of 'otation ot' The piercngnill of Fig. 1 conprisesa the pierced billet at the various points that pair of barrel-shapedobliquely-disposed work is applied to it to enlarge its diameter rolls 1which, with a mandrel 2 arranged and reduce its wall thickness. As inthe between them, form a piercing pass. A case of the nill of Fig. 1,the pass forned solid billet 3, such as shown in Fig. 3, enters by therolls 10 also has a converging and a the left end of the roll ass andleaves its diverging portion, but in neither of these right end in theform oi a pierced billet 4, portions is the pierced billet elongated. Insuch as illustrated in Fig. 4:. The piercing the converging portion ofthe pass, extendpasshas two portions, a converging portion 'ing from'theplane of the points 12 to the extending from the plane of points 5 whereplane of the points 13, the billet is gripped the solid billet isengaged by the rolls to the and pressed inwardly upon the head ofmanplane of points 6 where the rolls are of drel 11, but its wallthickness is not there greatest diameter, and a diverging portionreduced and the metal is only slightly extending from the plane ofpoints 6 to the worked. When in the diverging portion of plane of points7 where the pierced billet the pass, extending from the plane of thepasses beyond the nandrel'. In practice the points 13 to that of thepoints 14, the diamtaper of the rolls to form the converging pass eterof the billet is enlarged and its wall is only of such angularity as isnecessary to thickness diminished with effecting little, f produceenough grip between therolls and any, elongation. Accordingly,throughout the billet to force the billet forwardly onto the entire passthe cross sectional area ot the point of the mandrel which custonarilythe pierced billet remains unifo'rm. extends into the converging portionof the The solid billet 3 shown in Fig. 3, the pass. This conver `ncenecessarily produces i -ced billet, of Fig. 4, and the expandedsoneelongation o the billet, butthoroughgill t 15 of Fig 5 typicallyrepresent a out the major porti-on of the convcrging secblank-f -mingprocedur capable of being tion of the pass the billet is solid andtherea--i d out in th practice of this invention. fore elongationstresses do not so severely The ratio of the length to the diameter ofStress or unish the metal. solid billet 3 is greater than that used inthe In the iverging pass, the piercing rolls 1 customary practice, andthe percentage 1nand the mandrel 2 are so forned or tapered crease inlength of this billet to produce and adjusted that there is little, ifany, elonthe pierced billet 4 is less than in the cusgation of thepierced billet. Such'being the tomary practice. Furthermore, the excase,the cross sectional area of the pierced panded billet 15 of Fig. 5 is ofthe same, or portion of the billet remainsuniforn' in all substantially`the same, length as the pierced transverse planes from that passingthrough bill t 4 These views therefore show how, the points 6 to thatpassing through the in the preparation of a blank according to points 7at the end of the pass, or in other this invention, the blank s gven an1n mu n words, in all transverse planes in the divergelongation with anattendant dmnuton n working stresses placed upon the blank. By thusdiminishing the stresses, much less power is required, scrap losses arematerially reduced,' one of the causes of defective tubing is greatlyreduced if not entirely eliminated, and the labor and other cost ofmanufacture of tubing is materially reduced.

According to the provisions of the patent statutes, I have explained theprinciple and mode of operation of my invention, and' have illustratedand described a specific mannerin which it may be practiced. However, Idesire to have it understood that, within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed.

I claim as my invention:

1. The method of forming a blank for making a seamless tube, comprisingprogressively piercing a solid billet, and simultaneously expanding thediameter and reducing the Wall thickness of the pierced portion of thebillet while maintaining the cross sectional area of the major part ofthe pierced portion of the billet substantially uniform during theexpandng and reducing operation;

2. The method of forming a blank for making a seamless tube, comprisingprogressively piercing a solid billet, simultaneously expanding thediameter and reducing the wall thickness of the pierced portion ot' thebillet, then expanding the diameter and reducing the wall thickness ofthe pierced billet, and during both of the expanding and reducing,Operations maintaining the cross sectional area of the billetsubstantially uniform. r

3. The method of forinng a blank for making a seamless tube, comprisingpiercing a solid billet, and subsequently expanding the diameter andreducing the Wall thiokness of the pierced billet While maintaining thecross sectional area of the pierced billet substantially uniform.

In testimony whereof, I sign my name.

RALPH o. STIEFEL.

